and also that a black hole of mass \(M\)  should evaporate over a timescale of order \(t_{evap}\sim G^2 M^3\) .
These results lead directly to Hawking's information problem: any information about how the black hole was made lies deep in the interior of the black hole, which the semiclassical picture tells us is spacelike-separated from the near-horizon region where the radiation is being produced, and thus the evaporation process destroys this information in contradiction with the unitarity of quantum mechanics. It has sometimes been hoped that unitarity could be restored by “small corrections” to Hawking's calculation, but by now it is clear that no small modification of the semiclassical picture can restore unitarity [1]}. We thus need to either accept that the evaporation process is not unitary, which would itself lead to a violation of (REF ), or else that the semiclassical picture of spacetime is badly violated by the microscopic description of black holes. Said differently, the spacetime near black holes, and thus spacetime everywhere, must be emergent: it is not a fundamental part of the theory, and only exists in some situations and to some approximation. This topic has been the subject of a large amount of recent work, which was reviewed extensively in the white paper [2]} and whose main points we now summarize (see [2]} for many more references).
